胆汁酸代谢经典途径酶基因表达与豚鼠胆石病关系的研究

Study on the Association of Gene Expression of Cholesterol 7α- and Sterol 12α-Hydroxylase with Cholelithiasis in Guinea Pigs

目的：研究豚鼠肝脏胆汁酸代谢经典途径关键酶──胆固醇７α一羟化酶（ＣＹＰ７ａｌ）和甾醇１２α－羟化酶（ＣＹＰ８ｂ１） 的基因表达与胆汁脂质含量及胆固醇结石形成的关系。方法：采用点杂交技术检测对照组（ｎ＝８）（普通豚鼠饲料喂 养）、未成石组（ｎ＝１３）和成石组豚鼠（ｎ＝９）（致石饲料喂养）肝脏ＣＹＰ７ａｌ和ＣＹＰ８ｂ１ ｍＲＮＡ的相对含量，并对三组豚 鼠胆汁脂质成份进行检测和分析。结果： １、与对照组豚鼠（ｎ＝８）相比，成石组豚鼠（ｎ＝８）肝脏ＣＹＰ７ａ１ ｍＲＮＡ的相对 含量显著减少（０．３９±０．１９比０．７３±０．３６，Ｐ＝０．０３），ＣＹＰ７ａ１的ｍＲＮＡ相对量与胆汁胆固醇摩尔浓度、胆固醇在胆汁胆 固醇、胆汁酸和磷脂三者中的摩尔百分数、胆汁中胆汁酸摩尔浓度皆无明显相关。２、对照组（ｎ＝８）、未成石组（ｎ＝８）和 成石组豚鼠（ｎ＝８）肝脏ＣＹＰ８ｂ１ ｍＲＮＡ的相对含量无显著差异。３、未成石组（ｎ＝１３）和成石组豚鼠（ｎ＝９）胆汁胆固醇 浓度明显高于对照组（ｎ＝８），分别为：０．５０ｍｍｏｌ／Ｌ±０．０９ｍｍｏｌ／Ｌ比０．３９ｍｍｏｌ／Ｌ±０．１１ｍｍｏｌ／Ｌ，Ｐ＝０．０３；０．５０ｍｍｏｌ／Ｌ ±０．１０ｍｍｏｌ/

Objective: To study the association of gene expression of hepatic cholesterol 7α-hydroxylase (CYP7a1) and sterol 12α-hydroxylase (CYP8b1), the two key enzymes in classical pathway of bile acid biosynthesis, with the content of biliary lipid and the formation of cholesterol gallstones. Methods: The mRNA levels of hepatic CYP7a1 and CYP8b1 were detected by the method of dot blot in the control guinea pigs group(n＝8) fed with a normal diet, the non-lithogenic(n＝13) and lithogenic guinea pigs groups (n=9) fed with lithogenic diet. The concentrations of lipids in the bile were also measured and analyzed in these three groups. Results: Compared with the control group, the mRNA levels of hepatic CYP7a1 were significantly reduced in the gallstone group( 0.39±0.19 vs 0.73±0.36，P＝0.03). There was no correlation between the mRNA levels of hepatic CYP7a1 and the concentrations of cholesterol, bile acid, phospholipid and the percentage of cholesterol in the total biliary lipids of the bile. There was no s ignificant difference in the mRNA levels of hepatic CYP8b1 among the control group, the non-lithogenic group and the lithogenic group. The concentrations of cholesterol in the bile of guinea pigs in the non-lithogenic and the lithogenic groups were signif icantly higher than that of the guinea pigs in the control group(0.50mmol/L±0.09mmol/L vs 0.39mmol/L±0.11mmol/L， P＝0.03；0.50mmol/L±0.10mmol/L vs 0.39mmol/L±0.11mmol/L；P＝0.04, respectively). The concentrations of phospholipid in the bile of guinea pigs in the non-lithogenic and the lithogenic groups were significantly lower than that of guinea pigs in the contr ol group(0.30mmol/L±0.09mmol/L vs 0.48mmol/L±0.14mmol/L，P＝0.002；0.27mmol/L±0.11mmol/L vs 0.48mmol/L±0.14mmol/L，P＝0.003, respectively). Conclusions: The reduced gene expression of hepatic CYP7a1 may be the cause of the formation of gallstones in guinea pigs fed with lithogenic diets. Increased concentration of biliary cholesterol is an essential prerequisite for the formation of cholesterol gallstones in the guinea pigs. The decreased concentration of biliary phospholipid is another risk factor in the formation of cholesterol gallstones. The gene expression of CYP8b1 doesn't seem to play an important role in the formation of cholesterol gallstones of the guinea pigs.